Study On Ion Exchange Performance Of Hydrogen Peroxide Modified Layered Titanic Acid And Electrochemical Performance Of Its Derivatives

There exist two major problems among layered compound ion exchangers in that interlayer ions cannot be completely exchanged and exchanged for a long time.The key point to solve these problems is to modify the chemical structure in the interlayer so that more cations can easily ion exchange with interlayer ions,coming into the interlayer.As a layered compound with an opening structure,the interlayer of layered titanic acid can be easily modified.The chemical structure in the interlayer can be controlled by means of pillaring of interlayer and exfoliation-assembly,furthermore,fabricating products with special structure and morphology.The interlayer of layered titanic acid is H⁺or H₃O⁺,and the interlayer ions can be exchanged by the external metal cations via ion exchange reaction,obtaining layered titanic acid derivatives with different cations in the interlayer,which can be used as precursor to prepare multiphase titanate derivatives through the in situ topotactic transformation reaction.The obtained derivatives are widely used in the field of electrochemistry,photocatalysis,sensors,ferroelectric and etc.Therefore,in this thesis,various ion-exchanged products?such as Co-H₂O₂-HTO,Zn-H₂O₂-HTO?,plate-liked CoTiO₃/TiO₂ nanostructure,plate-liked NiTiO₃/TiO₂nanostructure,porous plate-liked TiO₂ as well as porous network Zn₂Ti₃O₈nanoarchitecture were prepared through the treatment of hydrogen peroxide,ion exchange and topotactic phase transformation using layered H_1.07Ti_1.73O₄ as precursor.The ion exchange and electrochemical performances were explored.And the evolution mechanism from precursor to products was revealed via the characterization of the structure of intermediate products and evolution of morphology.Layered peroxide H_1.07Ti_1.73O₄?H₂O₂-HTO?was prepared by hydrogen peroxide modification using layered H_1.07Ti_1.73O₄ as precursor.The ion exchange with M²⁺?M=Co,Ni,Cu,Zn?was carried out using H₂O₂-HTO as ion exchangers.The introduction of H₂O₂ in the interlayer of HTO makes more Mn²⁺come into the interlayer,finally obtaining ion-exchanged products with high molar ratio of M/Ti?Co/Ti=1.09:1.73,Ni/Ti=0.61:1.73,Cu/Ti=0.64:1.73,Zn/Ti=1.07:1.73?.As a comparison,the molar ratio of M/Ti in the ion-exchanged products obtained by HTO directly ion exchange with M²⁺is relatively low.?Co/Ti=0.18:1.73,Ni/Ti=0.08:1.73,Cu/Ti=0.24:1.73,Zn/Ti=0.51:1.73?.Furthermore,the capacity of ion exchange is not affected after the time of ion exchange is shortened.Namely,highly effective ion exchange is achieved.Layered peroxide H_1.07Ti_1.73O₄?H₂O₂-HTO?was prepared by hydrogen peroxide modification using layered H_1.07Ti_1.73O₄ as precursor.Plate-liked CoTiO₃/TiO₂ nanostructure,plate-liked CoTiO₃/TiO₂ nanostructure,plate-liked CuO/TiO₂ nanostructure and porous network Zn₂Ti₃O₈ nanoarchitecture were synthesized by ion exchange and in situ topotactic phase transformation reaction.And porous plate-liked TiO₂ was prepared by in situ etching CuO/TiO₂.the higher contents of ions in the interlayer of ion-exchanged products of H₂O₂-HTO leads to the higher content of titanates in the composites of titanate and titanium oxide by topotactic phase transformation of ion-exchanged products.In contrast,the lower contents of ion cause the lower contents of titanate after phase transformation,and the main phase is TiO₂.Porous network Zn₂Ti₃O₈ platelike nanoarchitecture was synthesized via in situ topotactic synthesis of the using layered H_1.07Ti_1.73O₄·H₂O as the precursor.The introduction of H₂O₂ in interlayer of HTO leads to access of more Zn²⁺ion into the interlayers and the formation of Zn²⁺ion-exchanged product with Zn/Ti molar ratio of 1.07:1.73 during ion exchange.This ion-exchanged product is in situ topotactically transformed into Zn₂Ti₃O₈ nanoarchitecture after heat-treatment,and the[110]-crystal-axis of Zn₂Ti₃O₈ nanoarchitecture is vertical to the basal plane of 2D nanoarchitecture.The H₂O₂ molecule within ion-exchanged product decomposes and escapes due to heat-treatment,resulting in the formation of the porous network structure similar to sponge.The pore size is about 10²0 nm.Moreover,the electrochemical investigation indicates that such porous network Zn₂Ti₃O₈ nanoarchitecture as Li-ion battery anode has its reversible capacity of 423 mAh·g^-1 during 100th cycle at the current density of100 mA·g^-1.It is wondrous that at the current density of 1 A·g^-1 during 1000cycles,its reversible capacity still remains 408 mAh·g^-1.